JPH08264879A - Distributed feedback semiconductor laser device - Google Patents
Distributed feedback semiconductor laser deviceInfo
- Publication number
- JPH08264879A JPH08264879A JP7062560A JP6256095A JPH08264879A JP H08264879 A JPH08264879 A JP H08264879A JP 7062560 A JP7062560 A JP 7062560A JP 6256095 A JP6256095 A JP 6256095A JP H08264879 A JPH08264879 A JP H08264879A
- Authority
- JP
- Japan
- Prior art keywords
- layer
- light
- periodic
- absorption layer
- light absorption
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
- H01S5/12—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region the resonator having a periodic structure, e.g. in distributed feedback [DFB] lasers
- H01S5/1228—DFB lasers with a complex coupled grating, e.g. gain or loss coupling
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/30—Structure or shape of the active region; Materials used for the active region
- H01S5/32—Structure or shape of the active region; Materials used for the active region comprising PN junctions, e.g. hetero- or double- heterostructures
- H01S5/323—Structure or shape of the active region; Materials used for the active region comprising PN junctions, e.g. hetero- or double- heterostructures in AIIIBV compounds, e.g. AlGaAs-laser, InP-based laser
- H01S5/32308—Structure or shape of the active region; Materials used for the active region comprising PN junctions, e.g. hetero- or double- heterostructures in AIIIBV compounds, e.g. AlGaAs-laser, InP-based laser emitting light at a wavelength less than 900 nm
- H01S5/32316—Structure or shape of the active region; Materials used for the active region comprising PN junctions, e.g. hetero- or double- heterostructures in AIIIBV compounds, e.g. AlGaAs-laser, InP-based laser emitting light at a wavelength less than 900 nm comprising only (Al)GaAs
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/30—Structure or shape of the active region; Materials used for the active region
- H01S5/32—Structure or shape of the active region; Materials used for the active region comprising PN junctions, e.g. hetero- or double- heterostructures
- H01S5/323—Structure or shape of the active region; Materials used for the active region comprising PN junctions, e.g. hetero- or double- heterostructures in AIIIBV compounds, e.g. AlGaAs-laser, InP-based laser
- H01S5/32308—Structure or shape of the active region; Materials used for the active region comprising PN junctions, e.g. hetero- or double- heterostructures in AIIIBV compounds, e.g. AlGaAs-laser, InP-based laser emitting light at a wavelength less than 900 nm
- H01S5/32333—Structure or shape of the active region; Materials used for the active region comprising PN junctions, e.g. hetero- or double- heterostructures in AIIIBV compounds, e.g. AlGaAs-laser, InP-based laser emitting light at a wavelength less than 900 nm based on InGaAsP
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、単一縦モードで発振す
る利得結合分布帰還型半導体レーザ装置（以下、「利得
結合ＤＦＢ−ＬＤ」と略す）に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gain-coupled distributed feedback semiconductor laser device (hereinafter abbreviated as "gain-coupled DFB-LD") which oscillates in a single longitudinal mode.
【０００２】[0002]
【従来の技術】利得結合ＤＦＢ−ＬＤは、優れた単一縦
モード発振が得られること、戻り光により雑音が生じに
くいことといった特徴を有している。波長１．３３μ
ｍ、１．５μｍを有する長波長の利得結合ＤＦＢ−ＬＤ
は超高速光通信用の光源として、概１μｍよりも短い波
長の利得結合ＤＦＢ−ＬＤは光計測装置・高速光伝送装
置・光記録装置の光源として重要である。2. Description of the Related Art A gain-coupled DFB-LD is characterized in that excellent single longitudinal mode oscillation is obtained and that noise is less likely to occur due to returning light. Wavelength 1.33μ
wavelength-coupled DFB-LD with m, 1.5 μm
Is important as a light source for ultra-high-speed optical communication, and a gain-coupled DFB-LD having a wavelength shorter than about 1 μm is important as a light source for optical measuring devices, high-speed optical transmission devices, and optical recording devices.
【０００３】利得結合ＤＦＢ−ＬＤは、誘導放出光を発
生する活性層がその誘導放出光に対して吸収を持たない
クラッド層に挟まれたダブルヘテロ接合構造を有してお
り、活性層近傍に回折格子を備えており、活性層が発生
する誘導放出光の利得が回折格子によって素子内部で位
置的に周期的に変化することによって光の分布帰還が生
じ、レーザ発振がもたらされる機構（これを「利得結
合」と呼ぶ）を有している。The gain-coupled DFB-LD has a double heterojunction structure in which an active layer that generates stimulated emission light is sandwiched between cladding layers that do not absorb the stimulated emission light. It is equipped with a diffraction grating, and the distributed feedback of the light is generated by the periodic variation of the gain of the stimulated emission light generated by the active layer inside the device due to the diffraction grating. (Referred to as "gain combination").
【０００４】回折格子によって誘導放出光の利得を周期
的に変化させる方法としては、活性層の利得そのものを
周期的に摂動させる方法（利得性回折格子）と、活性層
近傍に光吸収層を周期的に形成することによって実効的
に利得の周期的摂動が生じる構造（吸収性回折格子）と
が実現されている。後者に関しては、特公平６−７６２
４に基本となる構造が示されており、活発に研究されて
いる。As a method of periodically changing the gain of stimulated emission light by a diffraction grating, there is a method of periodically perturbing the gain itself of the active layer (gain diffraction grating), and a light absorption layer in the vicinity of the active layer. Structure (absorptive diffraction grating) that effectively causes periodic perturbation of gain is realized. Regarding the latter, Japanese Patent Publication No. 6-762
The basic structure is shown in 4 and is being actively studied.
【０００５】図７は活性層近傍に周期的な光吸収層を形
成することによって実効的に利得の周期的摂動が生じる
構造とした、従来の利得結合ＤＦＢ−ＬＤの構造を示す
図である（ＩＥＥＥ ＰＨＯＴＯＮＩＣＳ ＴＥＣＨＮ
ＯＬＯＧＹ ＬＥＴＴＥＲＳ，ＶＯＬ４，ＮＯ．７，１
９９２，Ｐ．６９２より）。すなわち、ｎ−ＧａＡｓ基
板７０１上にｎ−ＡｌＧａＡｓクラッド層７０２を１．
０μｍ、ｕｎ−ＧａＡｓ活性層７０３を０．０９μｍ、
ｐ−ＡｌＧａＡｓキャリアバリア層７０４を０．１μ
ｍ、ｐ−ＡｌＧａＡｓ第１ガイド層７０５を０．１μ
ｍ、ｎ−ＧａＡｓ光吸収層７０６を５０ｎｍ、有機金属
気相成長法（ＭＯＣＶＤ法）により連続的に結晶成長し
た後、二光束干渉露光法並びにウエットエッチング法に
より回折格子７０７を形成してｎ−ＧａＡｓ光吸収層７
０６を周期的に除去し、その上にｐ−ＡｌＧａＡｓ第２
ガイド層７０８を０．１μｍ、ｐ−ＡｌＧａＡｓクラッ
ド層７０９を１．０μｍ、ｐ−ＧａＡｓコンタクト層７
１０を０．５μｍの結晶再成長を行い、素子を作製して
いる。FIG. 7 is a diagram showing a structure of a conventional gain coupled DFB-LD having a structure in which a periodic perturbation of gain is effectively generated by forming a periodic light absorption layer in the vicinity of the active layer ( IEEE PHOTONICS TECHN
OLOGY LETTERS, VOL4, NO. 7, 1
992, P.I. (From 692). That is, the n-AlGaAs cladding layer 702 of 1. is formed on the n-GaAs substrate 701.
0 μm, un-GaAs active layer 703 0.09 μm,
0.1 μ of p-AlGaAs carrier barrier layer 704
m, p-AlGaAs first guide layer 705 0.1μ
After the crystal growth of the m, n-GaAs light absorption layer 706 of 50 nm by continuous metal organic chemical vapor deposition method (MOCVD method), the diffraction grating 707 is formed by the two-beam interference exposure method and the wet etching method to form n-. GaAs light absorption layer 7
06 is periodically removed, and p-AlGaAs second
The guide layer 708 is 0.1 μm, the p-AlGaAs cladding layer 709 is 1.0 μm, and the p-GaAs contact layer 7 is
10 is 0.5 μm in crystal regrowth to manufacture the device.
【０００６】図７における従来例では、吸収性回折格子
の吸収飽和を抑制する為に、導電型を反転した吸収層が
用いられている。In the conventional example shown in FIG. 7, in order to suppress absorption saturation of the absorptive diffraction grating, an absorption layer having a reversed conductivity type is used.
【０００７】[0007]
【発明が解決しようとする課題】高出力で半導体レーザ
を駆動させる場合には素子内部の光密度が非常に大きく
なる為、従来の利得結合ＤＦＢ−ＬＤにおいても光吸収
層に吸収飽和が生じ得る。光吸収層の吸収飽和が生じる
と、吸収性回折格子による利得結合が生じなくなる為に
単一縦モード発振特性を損なわれ、問題となる。When a semiconductor laser is driven at a high output, the light density inside the device becomes very large, so that absorption saturation may occur in the light absorption layer even in the conventional gain coupled DFB-LD. . When absorption saturation of the light absorption layer occurs, gain coupling due to the absorptive diffraction grating does not occur, and the single longitudinal mode oscillation characteristic is impaired, which becomes a problem.
【０００８】また、従来の構造では光吸収層として活性
層に比較的近い禁制帯幅を有する半導体層が用いられて
きた。この場合には、誘導放出光が周期的吸収層で吸収
されるときの吸収の程度を示す「吸収係数」が、吸収層
内の不純物添加量や活性層からの誘導放出光の波長の変
動に強く影響されることになる。その結果、作製される
素子の特性にばらつきが生じるほか、素子をレーザ発振
させる時、その出力によって光吸収層の吸収係数が大き
く変化し、安定した単一縦モード特性が確保されない問
題があった。Further, in the conventional structure, a semiconductor layer having a forbidden band width relatively close to that of the active layer has been used as the light absorption layer. In this case, the "absorption coefficient", which indicates the degree of absorption when the stimulated emission light is absorbed by the periodic absorption layer, depends on the amount of impurities added in the absorption layer and the fluctuation of the wavelength of the stimulated emission light from the active layer. It will be strongly influenced. As a result, the characteristics of the manufactured device vary, and when the device is oscillated, the absorption coefficient of the light absorption layer changes significantly due to the output, and stable single longitudinal mode characteristics cannot be ensured. .
【０００９】[0009]
【課題を解決するための手段】本発明に係る請求項１の
分布帰還型半導体レーザ装置は、活性層近傍に光分布帰
還を与える周期構造を備え、該周期構造が、前記活性層
から発生する誘導放出光に対する吸収係数が周期的に変
化する、周期的吸収層である利得結合分布帰還型半導体
レーザにおいて、前記誘導放出光のエネルギーｈνと、
前記周期的光吸収層の禁制帯幅Ｅgが、下記式（Ｉ）を
満たしてなることを特徴とするものである。According to a first aspect of the present invention, there is provided a distributed feedback semiconductor laser device having a periodic structure in the vicinity of an active layer for providing a distributed light feedback, and the periodic structure is generated from the active layer. In a gain-coupled distributed feedback semiconductor laser that is a periodic absorption layer in which the absorption coefficient for stimulated emission light changes periodically, the energy hν of the stimulated emission light is:
The forbidden band width E g of the periodic light absorption layer satisfies the following formula (I).
【００１０】[0010]
【数１】 [Equation 1]
【００１１】本発明に係る請求項２の分布帰還型半導体
レーザ装置は、前記周期的光吸収層がｎ型ＡｌxＧａ1-x
Ａｓ（０≦ｘ≦１）で形成され、かつ、その厚さが電子
のド・ブロイ波長よりも厚く、かつ、前記誘導放出光の
エネルギーｈνと前記周期的光吸収層の禁制帯幅Ｅgと
の差が０．１３ｅＶ以上であることを特徴とするもので
ある。According to a second aspect of the distributed feedback semiconductor laser device of the present invention, the periodic light absorption layer has n-type Al x Ga 1 -x.
Is formed of As (0 ≦ x ≦ 1), the thickness thereof is thicker than the de Broglie wavelength of electrons, the energy hν of the stimulated emission light and the forbidden band width E g of the periodic light absorption layer. Is 0.13 eV or more.
【００１２】本発明に係る請求項３の分布帰還型半導体
レーザ装置は、前記周期的光吸収層がｐ型ＡｌxＧａ1-x
Ａｓ（０≦ｘ≦１）で形成され、かつ、その厚さが電子
のド・ブロイ波長よりも厚く、かつ、前記誘導放出光の
エネルギーｈνと前記周期的光吸収層の禁制帯幅Ｅgと
の差が０．０８ｅＶ以上であることを特徴とするもので
ある。In a distributed feedback semiconductor laser device according to a third aspect of the present invention, the periodic light absorption layer is a p-type Al x Ga 1 -x.
Is formed of As (0 ≦ x ≦ 1), the thickness thereof is thicker than the de Broglie wavelength of electrons, the energy hν of the stimulated emission light and the forbidden band width E g of the periodic light absorption layer. Is 0.08 eV or more.
【００１３】本発明に係る請求項４の分布帰還型半導体
レーザ装置は、前記周期的光吸収層がｎ型Ｉｎ1-yＧａy
Ａｓ1-zＰz（０≦ｙ≦１、０≦ｚ≦１）で形成され、か
つ、その厚さが電子のド・ブロイ波長よりも厚く、か
つ、前記誘導放出光のエネルギーｈνと前記周期的光吸
収層の禁制帯幅Ｅgとの差が０．１５ｅＶ以上であるこ
とを特徴とするものである。In a distributed feedback semiconductor laser device according to a fourth aspect of the present invention, the periodic light absorption layer is an n-type In 1-y Ga y.
As 1-z P z (0 ≦ y ≦ 1, 0 ≦ z ≦ 1), the thickness thereof is thicker than the de Broglie wavelength of the electron, and the energy hν of the stimulated emission light and the The difference from the forbidden band width E g of the periodic light absorption layer is 0.15 eV or more.
【００１４】本発明に係る請求項５の分布帰還型半導体
レーザ装置は、前記周期的光吸収層がｐ型Ｉｎ1-yＧａy
Ａｓ1-zＰz（０≦ｙ≦１、０≦ｚ≦１）で形成され、か
つ、その厚さが電子のド・ブロイ波長よりも厚く、か
つ、前記誘導放出光のエネルギーｈνと前記周期的光吸
収層の禁制帯幅Ｅgとの差が０．１ｅＶ以上であること
を特徴とするものである。[0014] distributed feedback semiconductor laser device according to claim 5 of the present invention, the periodic light absorption layer is p-type In 1-y Ga y
As 1-z P z (0 ≦ y ≦ 1, 0 ≦ z ≦ 1), the thickness thereof is thicker than the de Broglie wavelength of the electron, and the energy hν of the stimulated emission light and the The difference from the forbidden band width E g of the periodic light absorption layer is 0.1 eV or more.
【００１５】[0015]
【作用】請求項１においては、周期的光吸収層の禁制帯
幅Ｅgが、下記式（Ｉ）を満たすことにより、前記周期
的吸収層の価電子帯の電子が、伝導帯における自由電子
が熱的に分布するエネルギーレベルよりも高いエネルギ
ーへ、前記誘導放出光によって励起されるように、周期
的光吸収層の材料が選択されることとなり、光吸収層に
おける吸収飽和が抑制される。According to the present invention, the band gap E g of the periodic light absorption layer satisfies the following formula (I), so that the electrons in the valence band of the periodic absorption layer become free electrons in the conduction band. The material of the periodic light-absorbing layer is selected so as to be excited by the stimulated emission light to an energy higher than the energy level at which is thermally distributed, and absorption saturation in the light-absorbing layer is suppressed.
【００１６】[0016]
【数１】 [Equation 1]
【００１７】請求項２においては、前記周期的光吸収層
がｎ型ＡｌxＧａ1-xＡｓ（０≦ｘ≦１）で形成され、か
つ、その厚さが電子のド・ブロイ波長よりも厚く、か
つ、前記誘導放出光のエネルギーｈνと前記周期的光吸
収層の禁制帯幅Ｅgとの差が０．１３ｅＶ以上であるこ
とにより、光吸収層における吸収飽和がより抑制される
ものである。According to a second aspect of the present invention, the periodic light absorption layer is formed of n-type Al x Ga 1-x As (0 ≦ x ≦ 1), and its thickness is greater than the de Broglie wavelength of electrons. Since the thickness h is large and the difference between the energy hν of the stimulated emission light and the forbidden band width E g of the periodic light absorption layer is 0.13 eV or more, absorption saturation in the light absorption layer is further suppressed. is there.
【００１８】請求項３においては、前記周期的光吸収層
がｐ型ＡｌxＧａ1-xＡｓ（０≦ｘ≦１）で形成され、か
つ、その厚さが電子のド・ブロイ波長よりも厚く、か
つ、前記誘導放出光のエネルギーｈνと前記周期的光吸
収層の禁制帯幅Ｅgとの差が０．０８ｅＶ以上であるこ
とにより、光吸収層における吸収飽和がより抑制される
ものである。According to a third aspect of the present invention, the periodic light absorption layer is formed of p-type Al x Ga 1-x As (0 ≦ x ≦ 1), and its thickness is larger than the electron de Broglie wavelength. Since the difference between the energy hν of the stimulated emission light and the forbidden band width E g of the periodic light absorption layer is 0.08 eV or more, absorption saturation in the light absorption layer is further suppressed. is there.
【００１９】請求項４においては、前記周期的光吸収層
がｎ型Ｉｎ1-yＧａyＡｓ1-zＰz（０≦ｙ≦１、０≦ｚ≦
１）で形成され、かつ、その厚さが電子のド・ブロイ波
長よりも厚く、かつ、前記誘導放出光のエネルギーｈν
と前記周期的光吸収層の禁制帯幅Ｅgとの差が０．１５
ｅＶ以上であることにより、光吸収層における吸収飽和
がより抑制されるものである。According to a fourth aspect of the present invention, the periodic light absorption layer is n-type In 1-y Ga y As 1-z P z (0 ≦ y ≦ 1, 0 ≦ z ≦.
1) and the thickness thereof is thicker than the de Broglie wavelength of electrons, and the energy hν of the stimulated emission light is
And the forbidden band width E g of the periodic light absorption layer is 0.15.
By being eV or more, absorption saturation in the light absorption layer is further suppressed.
【００２０】請求項５においては、前記周期的光吸収層
がｎ型Ｉｎ1-yＧａyＡｓ1-zＰz（０≦ｙ≦１、０≦ｚ≦
１）で形成され、かつ、その厚さが電子のド・ブロイ波
長よりも厚く、かつ、前記誘導放出光のエネルギーｈν
と前記周期的光吸収層の禁制帯幅Ｅgとの差が０．１ｅ
Ｖ以上であることにより、光吸収層における吸収飽和が
より抑制されるものである。In the present invention, the periodic light absorption layer is n-type In 1-y Ga y As 1-z P z (0 ≦ y ≦ 1, 0 ≦ z ≦.
1) and the thickness thereof is thicker than the de Broglie wavelength of electrons, and the energy hν of the stimulated emission light is
And the band gap E g of the periodic light absorption layer is 0.1e.
By being V or more, absorption saturation in the light absorption layer is further suppressed.
【００２１】このような作用をもたらす理由を、以下に
説明する。図８に、光吸収層の厚さが電子のド・ブロイ
波長（概１０ｎｍ）以上の時の、光吸収層のバンド構造
を示す。活性層から発せられる光（図８（ａ）ではｈν
で示されている。）が光吸収層で吸収される時（この時
にＥc−Ｅv＜ｈνとなることが吸収が生じる条件）、光
吸収層内でのキャリア（電子−正孔対）の生成を伴う。
このときに生成されるキャリアの一部は図８（ｂ）に示
される様に再結合消滅を起こすが、一部は定常的に伝導
帯に蓄積されることになる。この時に光吸収層内に蓄積
されることのできるキャリアの数には量子力学的に上限
があり、その上限を越えると、それ以上にはキャリアが
生成されなくなり、光吸収層における光吸収がもはや生
じなくなる。この状態を「過飽和吸収」または「吸収飽
和」と呼ぶ。光吸収層の伝導帯には、熱的に励起されて
いる自由電子が予め存在しており、光吸収によって生成
されるキャリアの上限を小さくする一つの要因となって
いる。The reason why such an action is brought about will be described below. FIG. 8 shows the band structure of the light absorption layer when the thickness of the light absorption layer is equal to or more than the de Broglie wavelength of electrons (approximately 10 nm). Light emitted from the active layer (hν in FIG. 8A)
Indicated by. Is absorbed in the light absorption layer (at this time, E c −E v <hν is a condition for absorption), it is accompanied by generation of carriers (electron-hole pairs) in the light absorption layer.
Some of the carriers generated at this time cause recombination and disappearance as shown in FIG. 8B, but some of them are constantly accumulated in the conduction band. At this time, there is a quantum mechanical upper limit to the number of carriers that can be accumulated in the light absorption layer, and if the upper limit is exceeded, no more carriers will be generated, and light absorption in the light absorption layer will no longer occur. It will not occur. This state is called "supersaturated absorption" or "absorption saturated". Free electrons that are thermally excited are present in the conduction band of the light absorption layer in advance, which is one of the factors that reduce the upper limit of carriers generated by light absorption.
【００２２】図９に過飽和吸収が生じた場合の利得結合
ＤＦＢ−ＬＤの電流−光出力特性の一例を示すが、光出
力が一定値Ｐsatを越えた時点で過飽和吸収が生じ、出
力がＡ→Ｂへと不連続に切り変わると共に、Ｂ→Ｃの間
では利得結合が生じないために単一縦モード特性が不良
となる。FIG. 9 shows an example of current-optical output characteristics of the gain-coupled DFB-LD when supersaturated absorption occurs. When the optical output exceeds a certain value P sat , supersaturated absorption occurs and the output becomes A. The switching from B to C is discontinuous, and gain coupling does not occur between B and C, so that the single longitudinal mode characteristic becomes defective.
【００２３】過飽和吸収を抑制する為の手段としては、
光吸収層に蓄積することができるキャリアの数の量子力
学的な上限（状態密度）をできるだけ大きくすることが
効果的である。つまり、光吸収層内で生成されるキャリ
アのエネルギーが、熱的に励起されている自由電子より
も大きければ、熱的に励起されている自由電子による状
態密度の低減の影響を受けず、過飽和吸収がより高出力
まで起こらなくなる作用をもたらせる。As means for suppressing supersaturated absorption,
It is effective to maximize the quantum mechanical upper limit (state density) of the number of carriers that can be accumulated in the light absorption layer. That is, if the energy of carriers generated in the light absorption layer is larger than that of the thermally excited free electrons, it is not affected by the reduction in the density of states due to the thermally excited free electrons, and the supersaturation It has the effect that absorption does not occur up to a higher output.
【００２４】熱的に励起されている自由電子は、伝導帯
の底（低エネルギー端部）から約０．１ｅＶの幅をもっ
て高エネルギー側へ裾を引きながら分布する。よって、
前記誘導放出光のエネルギーがｈνが周期的光吸収層の
禁制体幅Ｅgよりも概ね０．１ｅＶ以上大きければ、熱
的に励起されている自由電子による状態密度の低減の効
果を受けず、高出力まで吸収が飽和しないことが予測さ
れる。The thermally excited free electrons are distributed with a width of about 0.1 eV from the bottom of the conduction band (low energy end) while tailing to the high energy side. Therefore,
When the energy of the stimulated emission light hν is larger than the forbidden body width E g of the periodic light absorption layer by about 0.1 eV or more, the effect of reducing the density of states due to the thermally excited free electrons is not exerted, It is expected that absorption will not saturate up to high power.
【００２５】利得結合ＤＦＢ−ＬＤにおける種々の作製
パラメータ（利得結合定数など）を一定にしたまま、種
々の周期的光吸収層の禁制帯幅と誘導放出光のエネルギ
ーとの差をもつ素子を作製し、実験的に上記の事項を検
証したところ、ｎ型ＡｌxＧａ1-xＡｓ（０≦ｘ≦１）を
光吸収層とした場合には前記の差が０．１３ｅＶ以上の
時に、ｎ型ＡｌxＧａ1-xＡｓ（０≦ｘ≦１）を光吸収層
とした場合には前記の差が０．０８ｅＶ以上の時に高出
力まで吸収が飽和しないことが確かめられた。An element having various differences between the forbidden band width of the periodic light absorption layer and the energy of the stimulated emission light is produced while the various production parameters (gain coupling constant etc.) in the gain coupled DFB-LD are kept constant. However, when the above items are experimentally verified, when n-type Al x Ga 1-x As (0 ≦ x ≦ 1) is used as the light absorption layer, when the difference is 0.13 eV or more, It was confirmed that when the type Al x Ga 1-x As (0 ≦ x ≦ 1) was used as the light absorbing layer, the absorption was not saturated up to high output when the difference was 0.08 eV or more.
【００２６】ｎ型の半導体層を光吸収層に用いた場合の
方が過飽和吸収を生じやすいのは、ドナー不純物レベル
から伝導帯へ熱的に励起される自由電子が多いことの影
響である。The fact that supersaturated absorption is more likely to occur when an n-type semiconductor layer is used as the light absorption layer is due to the fact that many free electrons are thermally excited from the donor impurity level to the conduction band.
【００２７】また、同様にしてＩｎ1-yＧａyＡｓ1-zＰz
（０≦ｙ≦１、０≦ｚ≦１）系に対しては、ｎ型の層を
光吸収層とした場合には前記の差が０．１５ｅＶ以上の
時に、ｐ型の層を光吸収層とした場合には前記の差が
０．０８ｅＶ以上の時に高出力まで吸収が飽和しないこ
とが確かめられた。[0027] In the same manner In 1-y Ga y As 1 -z P z
For the (0 ≦ y ≦ 1, 0 ≦ z ≦ 1) system, when the n-type layer is used as a light absorbing layer, the p-type layer absorbs light when the difference is 0.15 eV or more. It was confirmed that the absorption did not saturate up to high output when the difference was 0.08 eV or more when the layer was used.
【００２８】ＡｌＧａＡｓ系の場合よりもＩｎＧａＡｓ
Ｐ系の場合の方が過飽和吸収を生じやすいのは、ＩｎＧ
ａＡｓＰ系の方が電子の有効質量が小さいために、伝導
帯の状態密度が小さいことによる。InGaAs compared to AlGaAs
InG is more likely to cause supersaturation absorption in the case of P type.
This is because the effective mass of electrons is smaller in the aAsP system, and thus the density of states of the conduction band is smaller.
【００２９】上記請求項２、３においては他の作用があ
る。即ち、活性層から発生する誘導放出光に対する周期
的光吸収層の吸収係数が周期的光吸収層内の不純物密度
や光エネルギーに依存することがなくなり、作製される
素子の特性にばらつきが生じないほか、素子をレーザ発
振させた時にその出力や温度変化によって光吸収層の吸
収係数が変化することが無くなり、安定した素子特性が
再現性良く得られるものである。In the above-mentioned claims 2 and 3, there is another action. That is, the absorption coefficient of the periodic light absorption layer for the stimulated emission light generated from the active layer does not depend on the impurity density or the light energy in the periodic light absorption layer, and the characteristics of the manufactured device do not vary. In addition, the absorption coefficient of the light absorption layer does not change due to changes in the output or temperature of the device when the device is oscillated, and stable device characteristics can be obtained with good reproducibility.
【００３０】この作用をもたらす理由を、周期的吸収層
がＧａＡｓの場合を例に挙げて説明する。図１０（ａ）
に、バルク状の（つまり厚さが電子のド・ブロイ波長以
上となっている）ｎ型ＧａＡｓ、（ｂ）にｐ型ＧａＡｓ
の吸収係数の光エネルギー依存性を示す（Ｈ．Ｃ．Ｃａ
ｓｅｙ，Ｊｒ．ａｎｄ Ｍ．Ｂ．Ｐａｎｉｓｈ：Ｈｅｔ
ｅｒｏｓｔｒｕｃｔｕｒｅ Ｌａｓｅｒｓ，Ａｃａｄｅ
ｍｉｃ Ｐｒｅｓｓ（１９７８）より）。半導体レーザ
の場合には添加する不純物密度は５×１０17〜２×１０
18ｃｍ-1程度に制御されており、この範囲においては、
光エネルギーとしてｎ型に対しては概１．５５ｅＶ、ｐ
型に対しては概１．５０ｅＶ以下に対してＧａＡｓの吸
収係数が不純物密度に大きく依存する。その結果、再現
性良く予め設計された吸収係数が得られにくいと同時
に、ＧａＡｓの吸収係数が光エネルギーに大きく依存す
ることになり、素子間やロット間で周期的吸収層の吸収
係数がばらつき、素子特性の再現性に問題が生じる。一
方で光エネルギーがｎ型に対しては概１．５５ｅＶ、ｐ
型に対しては概１．５０ｅＶ以上の光に対しては吸収係
数は不純物密度や光エネルギーに依存せずにほぼ一定値
１２０００〜１５０００ｃｍ-1の安定した値が確保さ
れ、素子作製時の再現性、素子動作の安定性に優れる構
造となる。ＧａＡｓの禁制帯幅は１．４２ｅＶであるこ
とから、活性層と吸収層との禁制帯幅の差が概０．１３
ｅＶ以上あれば上記の効果が期待できることになる。特
に、不純物密度による吸収係数の変動が大きいｎ型Ｇａ
Ａｓ（図１０（ａ））では効果が大きい。The reason why this effect is brought about will be explained by taking the case where the periodic absorption layer is GaAs as an example. Figure 10 (a)
Bulk-type (that is, the thickness is equal to or more than the de Broglie wavelength of the electron) n-type GaAs, (b) p-type GaAs
Shows the dependence of absorption coefficient of light energy on light energy (HC Ca
sey, Jr. and M.D. B. Panish: Het
erostructure Lasers, Acade
mic Press (1978)). In the case of a semiconductor laser, the impurity density added is 5 × 10 17 to 2 × 10 5.
It is controlled to about 18 cm -1 , and in this range,
About 1.55 eV, p for n-type as light energy
For the type, the absorption coefficient of GaAs largely depends on the impurity density for approximately 1.50 eV or less. As a result, it is difficult to obtain a pre-designed absorption coefficient with good reproducibility, and at the same time, the absorption coefficient of GaAs largely depends on the light energy, and the absorption coefficient of the periodic absorption layer varies between elements and lots. There is a problem in reproducibility of element characteristics. On the other hand, the light energy is about 1.55 eV for p-type, p
The absorption coefficient for the mold is about 1.50 eV or more, and the absorption coefficient does not depend on the impurity density or the light energy, and a stable value of 12000 to 15000 cm -1 is secured. Structure and stability of device operation. Since the forbidden band width of GaAs is 1.42 eV, the difference between the forbidden band widths of the active layer and the absorption layer is about 0.13.
If it is eV or more, the above effect can be expected. In particular, n-type Ga, which has a large variation in absorption coefficient depending on the impurity density,
The effect is large with As (FIG. 10A).
【００３１】[0031]
【実施例】図１は本発明の第一の実施例の分布帰還型半
導体レーザ装置の構造を示す図である。1 is a diagram showing the structure of a distributed feedback semiconductor laser device according to a first embodiment of the present invention.
【００３２】まず、ｎ−ＧａＡｓ基板１０１上にｎ−Ａ
ｌ0.5Ｇａ0.5Ａｓクラッド層１０２を１μｍ、ｕｎ−Ａ
ｌ0.1Ｇａ0.9Ａｓ活性層１０３を０．０８μｍ、ｐ−Ａ
ｌ0.45Ｇａ0.55Ａｓキャリアバリア層１０４を０．２μ
ｍ、ｐ−Ａｌ0.2Ｇａ0.8Ａｓガイド層１０５を０．０５
μｍ、ｎ−ＧａＡｓ光吸収層１０６を３０ｎｍ、第一回
目のエピタキシャル成長により形成する。続いて、成長
層の最上層である光吸収層１０６上に二光束干渉露光に
よりピッチ０．３６μｍを有する格子状のレジストマス
クを得る。次にこのレジストマスクを用い、塩酸／過酸
化水素水／純水の混液によるウエットエッチングにより
光吸収層１０６が不連続になるようにエッチングし、三
次の矩形形状回折格子を作製する。このときの回折格子
のデューティは、光吸収層による吸収損失を抑える為に
０．２程度の低デューティになるように作製されてい
る。次にこの上に第二回目のエピタキシャル成長により
ｐ−Ａｌ0.7Ｇａ0.3Ａｓ上クラッド層１０７を０．８μ
ｍ、ｐ+−ＧａＡｓコンタクト層１０８を０．５μｍを
第二回目のエピタキシャル成長により形成する。First, n-A is formed on the n-GaAs substrate 101.
1 0.5 Ga 0.5 As clad layer 102 of 1 μm, un-A
l 0.1 Ga 0.9 As active layer 103 of 0.08 μm, p-A
l 0.45 Ga 0.55 As carrier barrier layer 104 is 0.2 μm
m, p-Al 0.2 Ga 0.8 As guide layer 105 to 0.05
A 30 μm thick n-type GaAs light absorption layer 106 is formed by the first epitaxial growth. Subsequently, a lattice-shaped resist mask having a pitch of 0.36 μm is obtained on the light absorption layer 106, which is the uppermost layer of the growth layer, by two-beam interference exposure. Next, using this resist mask, the light absorption layer 106 is etched by wet etching with a mixed solution of hydrochloric acid / hydrogen peroxide solution / pure water so that the light absorption layer 106 becomes discontinuous, thereby forming a cubic rectangular diffraction grating. The duty of the diffraction grating at this time is made to be a low duty of about 0.2 in order to suppress absorption loss by the light absorption layer. Then, a p-Al 0.7 Ga 0.3 As upper clad layer 107 is 0.8 μm on this by the second epitaxial growth.
A 0.5 μm thick m, p + -GaAs contact layer 108 is formed by the second epitaxial growth.
【００３３】次に、ｐ+−ＧａＡｓコンタクト層１０８
上にプラズマＣＶＤ法により窒化珪素の絶縁膜１０９を
約０．２μｍ形成し、この窒化珪素の絶縁膜上へのホト
リソグラフィーと緩衝フッ酸によるエッチングを用いて
幅１０μｍのストライプ溝を空けた後、全面にＡｕＺｎ
の電極１１０を形成する。基板の厚さを約１００μｍに
まで薄層化した後、裏面にはＡｕＧｅ／Ｎｉ電極１１１
を形成し、素子全体を４００℃で３分間の加熱処理をす
ることにより、素子が完成する。Next, the p + -GaAs contact layer 108
An insulating film 109 of silicon nitride is formed to a thickness of about 0.2 μm by a plasma CVD method, and a stripe groove having a width of 10 μm is formed on the insulating film of silicon nitride by photolithography and etching with buffer hydrofluoric acid. AuZn on the entire surface
The electrode 110 of is formed. After reducing the thickness of the substrate to about 100 μm, an AuGe / Ni electrode 111 is formed on the back surface.
Is formed, and the whole element is heat-treated at 400 ° C. for 3 minutes to complete the element.
【００３４】ＡｌＧａＡｓ材料系を用いた本実施例で
は、活性層と光吸収層の混晶比の差が０．１となってお
り、誘導放出光のエネルギー（波長８００ｎｍ→エネル
ギー１．５５ｅＶに相当）と光吸収層との禁制帯幅
（１．４２ｅＶ）の差は０．１３ｅＶに対応する。本素
子では、吸収層の過飽和吸収によって生じる光出力−電
流特性の不連続は光出力５０ｍＷ以上まで見られず、高
出力まで安定した単一軸モードでの発振が確認された。In this embodiment using the AlGaAs material system, the difference in the mixed crystal ratio between the active layer and the light absorption layer is 0.1, which corresponds to the energy of stimulated emission light (wavelength 800 nm → energy 1.55 eV). ) And the band gap (1.42 eV) of the light absorption layer correspond to 0.13 eV. In this device, discontinuity of light output-current characteristics caused by supersaturated absorption of the absorption layer was not observed up to light output of 50 mW or more, and stable oscillation in a single axis mode was confirmed up to high output.
【００３５】本実施例に示した構造において光吸収層の
Ａｌ混晶比をさまざまな値に変更した素子を作製し、周
期的光吸収層の禁制帯幅と誘導放出光のエネルギーとの
差であるΔＥgと、光出力２０ｍＷ以下において過飽和
吸収による特性劣化が見られた素子の割合との相関を調
べた結果を図２に示す。Ａｌ混晶比の差が０．１以上、
つまりΔＥgが０．１３ｅＶ以上の時に光出力２０ｍＷ
以下において過飽和吸収が生じる素子の割合は零となっ
ていることが実験的に確かめられた。光記録装置の光源
としてＤＦＢ−ＬＤを使用する場合、少なくても２０ｍ
Ｗの出力が要求され、本実施例の素子ではこの要求を満
足する特性が得られている。なお、これらの素子におい
ては、ΔＥgを変更しても他の設計的パラメータ（利得
結合定数、活性層光閉じ込め係数等）が一定となるよう
に作製されている。In the structure shown in this example, devices were produced in which the Al mixed crystal ratio of the light absorption layer was changed to various values, and the difference between the forbidden band width of the periodic light absorption layer and the energy of stimulated emission light was produced. FIG. 2 shows the result of examining the correlation between a certain ΔE g and the ratio of the elements in which the characteristic deterioration due to the supersaturation absorption was observed at the optical output of 20 mW or less. The difference in Al mixed crystal ratio is 0.1 or more,
That is, when ΔE g is 0.13 eV or more, the optical output is 20 mW
In the following, it was experimentally confirmed that the ratio of elements causing supersaturation absorption was zero. When using the DFB-LD as the light source of the optical recording device, at least 20 m
An output of W is required, and the element of this embodiment has characteristics satisfying this requirement. It should be noted that these elements are manufactured such that other design parameters (gain coupling constant, active layer optical confinement coefficient, etc.) are constant even if ΔE g is changed.
【００３６】図３は本発明の第二の実施例の分布帰還型
半導体レーザ装置の構造を示す図である。FIG. 3 is a diagram showing the structure of the distributed feedback semiconductor laser device of the second embodiment of the present invention.
【００３７】まず、ｎ−ＧａＡｓ基板３０１上にｎ−Ａ
ｌ0.6Ｇａ0.4Ａｓクラッド層３０２を１μｍ、ｕｎ−Ａ
ｌ0.13Ｇａ0.87Ａｓ活性層３０３を０．０８μｍ、ｐ−
Ａｌ0.5Ｇａ0.5Ａｓキャリアバリア層３０４を０．２μ
ｍ、ｐ−Ａｌ0.25Ｇａ0.75Ａｓ第一ガイド層３０５を
０．１μｍを第一回目のエピタキシャル成長により形成
する。続いて、成長層の最上層であるガイド層３０５上
に高屈折率を有するプリズムを通した二光束干渉露光に
よりピッチ０．１２μｍを有する格子状のレジストマス
クを得る。次にこのレジストマスクを用い、ウエットエ
ッチングによりガイド層３０５をエッチングすることに
より、回折格子を得る。次にこの上に第二回目のエピタ
キシャル成長によりバッファ層となるｐ−Ａｌ0.2 5Ｇａ
0.75Ａｓ第二ガイド層３０６を５ｎｍ、ｐ−ＧａＡｓ光
吸収層３０７を２５ｎｍ成長する。このときＧａＡｓは
回折格子の表面全体を覆うものの、三角形状の回折格子
の谷間に特に厚く結晶成長し、回折格子の凸凹に応じて
光吸収層の層厚が周期変化することになる。さらに連続
的にｐ−Ａｌ0.75Ｇａ0.25Ａｓ上クラッド層３０８を
０．８μｍ、ｐ+−ＧａＡｓコンタクト層３０９を０．
５μｍを第二回目のエピタキシャル成長により形成す
る。First, n-A is formed on the n-GaAs substrate 301.
1 0.6 Ga 0.4 As clad layer 302 of 1 μm, un-A
l 0.13 Ga 0.87 As active layer 303 0.08 μm, p-
Al 0.5 Ga 0.5 As carrier barrier layer 304 with 0.2μ
An m, p-Al 0.25 Ga 0.75 As first guide layer 305 is formed to a thickness of 0.1 μm by the first epitaxial growth. Then, a two-beam interference exposure through a prism having a high refractive index is performed on the guide layer 305 which is the uppermost layer of the growth layer to obtain a grid-shaped resist mask having a pitch of 0.12 μm. Next, using this resist mask, the guide layer 305 is etched by wet etching to obtain a diffraction grating. Then p-Al 0.2 5 Ga serving as a buffer layer by the second round of epitaxially grown on this
A 0.75 As second guide layer 306 is grown to a thickness of 5 nm and a p-GaAs light absorption layer 307 is grown to a thickness of 25 nm. At this time, GaAs covers the entire surface of the diffraction grating, but crystal growth grows particularly thickly in the valleys of the triangular diffraction grating, and the layer thickness of the light absorption layer changes periodically according to the unevenness of the diffraction grating. Further, the p-Al 0.75 Ga 0.25 As upper clad layer 308 was 0.8 .mu.m, and the p.sup . + -GaAs contact layer 309 was continuously formed with a thickness of 0.
5 μm is formed by the second epitaxial growth.
【００３８】次に、ｐ+−ＧａＡｓコンタクト層３０８
上にプラズマＣＶＤ法により窒化珪素の絶縁膜３１０を
約０．２μｍ形成し、この窒化珪素の絶縁膜上にホトリ
ソグラフィーと緩衝フッ酸によるエッチングを用いて幅
８μｍのストライプ状の溝を空けた後、全面にＡｕＺｎ
の電極３１１を形成する。基板を厚さ約１００μｍにま
で薄層化した後、裏面にはＡｕＧｅ／Ｎｉ電極３１２を
形成し、素子全体を４００℃で加熱処理することによ
り、素子が完成する。Next, the p + -GaAs contact layer 308 is formed.
After forming an insulating film 310 of silicon nitride of about 0.2 μm by plasma CVD on the insulating film of silicon nitride, a stripe-shaped groove having a width of 8 μm was formed on the insulating film of silicon nitride by photolithography and etching with buffer hydrofluoric acid. , AuZn on the entire surface
The electrode 311 of is formed. After thinning the substrate to a thickness of about 100 μm, an AuGe / Ni electrode 312 is formed on the back surface, and the whole element is heat-treated at 400 ° C. to complete the element.
【００３９】ＡｌＧａＡｓ材料系を用いた本実施例で
は、活性層３０３と光吸収層３０７の混晶比の差が０．
１３となっており、これは誘導放出光のエネルギー（波
長７８０ｎｍ→エネルギー１．５９ｅＶに相当）と光吸
収層との禁制帯幅（１．４２ｅＶ）の差が０．１７ｅＶ
であることに対応する。本素子では、吸収層の過飽和吸
収によって生じる光出力−電流特性の不連続は光出力１
００ｍＷ以上まで見られず、高出力まで安定した単一軸
モードでの発振が確認された。In this embodiment using the AlGaAs material system, the difference in the mixed crystal ratio between the active layer 303 and the light absorption layer 307 is 0.
The difference between the energy of stimulated emission light (wavelength 780 nm → energy of 1.59 eV) and the forbidden band width (1.42 eV) of the light absorption layer is 0.17 eV.
Corresponding to In this device, the discontinuity of the light output-current characteristics caused by the supersaturated absorption of the absorption layer is
Oscillation in a single axis mode, which was stable up to a high output, was confirmed without being observed up to more than 00 mW.
【００４０】本実施例に示した構造において光吸収層の
Ａｌ混晶比をさまざまな値に変更した素子を作製し、周
期的光吸収層の禁制帯幅と誘導放出光のエネルギーとの
差であるΔＥgと、光出力２０ｍＷ以下において過飽和
吸収による特性劣化が見られた素子の割合との相関を調
べた結果を図４に示す。ΔＥgが０．０８ｅＶ以上の時
に光出力２０ｍＷ以下において過飽和吸収が生じる素子
の割合は零となっていることが実験的に確かめられた。
なお、これらの素子においては、ΔＥgを変更しても他
の設計的パラメータ（利得結合定数、活性層光閉じ込め
係数等）が一定となるように作製されている。In the structure shown in this example, devices were produced in which the Al mixed crystal ratio of the light absorption layer was changed to various values, and the difference between the forbidden band width of the periodic light absorption layer and the energy of stimulated emission light was produced. FIG. 4 shows the result of examining the correlation between a certain ΔE g and the ratio of the elements in which the characteristic deterioration due to the supersaturation absorption was observed at the optical output of 20 mW or less. It was experimentally confirmed that when ΔE g is 0.08 eV or more, the ratio of the elements in which supersaturation absorption occurs at an optical output of 20 mW or less is zero.
It should be noted that these elements are manufactured such that other design parameters (gain coupling constant, active layer optical confinement coefficient, etc.) are constant even if ΔE g is changed.
【００４１】図５は本発明の第三の実施例の分布帰還型
半導体レーザ装置の構造を示す図である。FIG. 5 is a diagram showing the structure of the distributed feedback semiconductor laser device of the third embodiment of the present invention.
【００４２】この実施例は、まず、ｎ−ＩｎＰ基板５０
１上にｎ−ＩｎＰ第一下クラッド層５０２を０．５μ
ｍ、ｎ−ＩｎＧａＡｓＰ（Ｅg＝０．８０ｅＶ）光吸収
層５０３を２５ｎｍ、第一回目のエピタキシャル成長に
より形成する。続いて、成長層の最上層である光吸収層
５０３上に二光束干渉露光法とウエットエッチングによ
り一次の矩形形状回折格子（ピッチ約０．２４μｍ）を
作製する。次にこの上に第二回目のエピタキシャル成長
によりｎ−ＩｎＰ第二下クラッド層５０４を０．３μ
ｍ、ｕｎ−ＩｎＧａＡｓＰ（λ＝１．３μｍ→エネルギ
ー０．９５ｅＶに相当）活性層５０５を０．１μｍ、ｐ
−ＩｎＰ上クラッド層５０６を１μｍ、Ｐ+−ＩｎＧａ
Ａｓコンタクト層５０７を０．５μｍ、第二回目のエピ
タキシャル成長により形成する。In this embodiment, first, the n-InP substrate 50 is used.
N-InP first lower cladding layer 502 on top of 0.5
An m, n-InGaAsP (E g = 0.80 eV) light absorption layer 503 is formed at 25 nm by the first epitaxial growth. Subsequently, a first-order rectangular diffraction grating (pitch of about 0.24 μm) is formed on the light absorption layer 503, which is the uppermost layer of the growth layer, by a two-beam interference exposure method and wet etching. Next, an n-InP second lower clad layer 504 having a thickness of 0.3 μm is formed thereon by the second epitaxial growth.
m, un-InGaAsP (λ = 1.3 μm → corresponding to energy 0.95 eV) active layer 505 of 0.1 μm, p
-InP upper clad layer 506 is 1 μm, P + -InGa
An As contact layer 507 having a thickness of 0.5 μm is formed by the second epitaxial growth.
【００４３】次に、ホトリソグラフィーを用いて幅３μ
ｍのストライプ状のレジストマスクを形成し、ウエット
エッチングを用いて活性層の上部から０．３μｍの位置
までコンタクト層５０７と上クラッド層５０６をエッチ
ングしてリッジ形状にした後、表面全面にプラズマＣＶ
Ｄ法により窒化珪素の絶縁膜５０８を約０．２μｍ形成
し、リッジの頂上の絶縁膜だけを除去する。最後に基板
を厚さ約１００μｍにまで薄層化し、表面、裏面に電極
５０９，５１０を真空蒸着して、素子が完成する。Next, a width of 3 μm is obtained by using photolithography.
After forming a stripe-shaped resist mask of m, the contact layer 507 and the upper cladding layer 506 are etched into a ridge shape by wet etching to a position of 0.3 μm from the upper part of the active layer, and then plasma CV is formed on the entire surface.
An insulating film 508 of silicon nitride is formed to a thickness of about 0.2 μm by the D method, and only the insulating film on the top of the ridge is removed. Finally, the substrate is thinned to a thickness of about 100 μm, and electrodes 509 and 510 are vacuum-deposited on the front and back surfaces to complete the device.
【００４４】吸収層の可飽和吸収によって生じる光出力
−電流特性の不連続は、光出力５０ｍＷ以上まで見られ
ず、安定した単一軸モードでの発振が確認された。No discontinuity in the optical output-current characteristics caused by saturable absorption of the absorption layer was observed up to an optical output of 50 mW or more, and stable oscillation in a single axis mode was confirmed.
【００４５】本実施例に示した構造において、光吸収層
の導電型、及び、光吸収層の禁制帯幅をさまざまな値に
変更した素子を作製し、周期的光吸収層の禁制帯幅と誘
導放出光のエネルギーとの差であるΔＥgと、光出力２
０ｍＷ以下において過飽和吸収による特性劣化が見られ
た素子の割合との相関を調べた結果を図６に示す。ｎ型
の光吸収層を用いた場合にはΔＥgが０．１５ｅＶ以上
の時に、ｐ型の光吸収層を用いた場合にはΔＥgが０．
１ｅＶ以上の時に、光出力２０ｍＷ以下において過飽和
吸収が生じる素子の割合は零となっていることが実験的
に確かめられた。なお、これらの素子においては、ΔＥ
gを変更しても他の設計的パラメータ（格子定数、利得
結合定数、活性層光閉じ込め係数等）が一定となるよう
に作製されている。In the structure shown in this example, an element was prepared in which the conductivity type of the light absorption layer and the forbidden band width of the light absorption layer were changed to various values, and the forbidden band width of the periodic light absorption layer was changed. ΔE g , which is the difference from the energy of the stimulated emission light, and the optical output 2
FIG. 6 shows the result of examining the correlation with the ratio of the elements in which the characteristic deterioration due to the supersaturation absorption was observed at 0 mW or less. When the n-type light absorbing layer is used, ΔE g is 0.15 eV or more, and when the p-type light absorbing layer is used, ΔE g is 0.
It has been experimentally confirmed that the ratio of the elements in which supersaturation absorption occurs at an optical output of 20 mW or less is zero at 1 eV or more. In these elements, ΔE
Even if g is changed, other design parameters (lattice constant, gain coupling constant, active layer optical confinement coefficient, etc.) are made constant.
【００４６】本発明において、吸収係数が周期的に変化
する構造を含む利得結合ＤＦＢ−ＬＤであれば、その材
料系は上記実施例のものに限定されるものでは無く、
（Ａｌ，Ｇａ，Ｉｎ）（Ｐ，Ａｓ，Ｎ）や（Ｚｎ，Ｍ
ｇ，Ｃｄ）（Ｓ，Ｓｅ）等を含む他の材料系に対しても
本発明を適用することができる。また、活性層が量子井
戸構造であっても問題はない。また、光吸収層の配置に
は限定されないことは言うまでもない。さらに、光伝搬
領域に沿ったストライプ状の領域の形状や作製方法に限
定が生じるものでは無い。また、屈折率の摂動と利得
（損失）の摂動との周期が等しく位相がずれている構造
や、周期的光吸収層を光伝搬領域に沿ったストライプ状
の領域の外側に配置する構造に対しても本発明を適用す
ることができる。In the present invention, as long as it is a gain coupled DFB-LD including a structure in which the absorption coefficient changes periodically, its material system is not limited to that of the above embodiment,
(Al, Ga, In) (P, As, N) and (Zn, M
The present invention can be applied to other material systems including g, Cd) (S, Se) and the like. There is no problem even if the active layer has a quantum well structure. Needless to say, the arrangement of the light absorption layer is not limited. Furthermore, the shape of the stripe-shaped region along the light propagation region and the manufacturing method are not limited. In addition, for structures where the perturbation of the refractive index and the perturbation of the gain (loss) are equal and out of phase, or where the periodic light absorbing layer is arranged outside the stripe-shaped region along the light propagation region However, the present invention can be applied.
【００４７】[0047]
【発明の効果】請求項１の分布帰還型半導体レーザによ
れば、周期的吸収層の価電子帯の電子が、伝導帯におけ
る自由電子が熱的に分布するエネルギーレベルよりも高
いエネルギーへ、前記誘導放出光によって励起されるよ
うに、周期的光吸収層の材料が選択されていることによ
り、光吸収層における吸収飽和を抑制するものである。
その結果、高出力時にも安定した単一縦モード特性を有
する構造を得ることができる。また、上記の構成は、活
性層から発生する誘導放出光よりも周期的吸収層の禁制
帯幅を一定値以上大きくすることによって達成され、効
果的に過飽和吸収を抑制することができる。According to the distributed feedback semiconductor laser of the first aspect of the invention, the electrons in the valence band of the periodic absorption layer have a higher energy level than the energy level at which the free electrons in the conduction band are thermally distributed. The material of the periodic light absorption layer is selected so as to be excited by the stimulated emission light, thereby suppressing absorption saturation in the light absorption layer.
As a result, it is possible to obtain a structure having a stable single longitudinal mode characteristic even at high output. Further, the above configuration is achieved by making the forbidden band width of the periodic absorption layer larger than the stimulated emission light generated from the active layer by a certain value or more, and the supersaturated absorption can be effectively suppressed.
【００４８】請求項２、３、４、５の分布帰還型半導体
レーザによれば、前記請求項１の効果をより一層最適に
得ることが可能となる。According to the distributed feedback semiconductor laser of the second aspect, the third aspect, the fourth aspect, the fifth aspect, the effect of the first aspect can be obtained more optimally.
【００４９】また、請求項２、３の分布帰還型半導体レ
ーザによれば、活性層と周期的吸収層との禁制帯幅の差
が大きい場合、周期的吸収層の吸収係数が不純物密度や
光エネルギーによって変動することなく、安定した特性
を持つ素子を再現性良く作製することが可能となる。According to the distributed feedback semiconductor lasers of the second and third aspects, when the difference in the forbidden band width between the active layer and the periodic absorption layer is large, the absorption coefficient of the periodic absorption layer has an impurity density or an optical density. It is possible to fabricate an element having stable characteristics with good reproducibility without changing with energy.
【図１】実施例１の利得結合ＤＦＢ−ＬＤを示す図であ
る。FIG. 1 is a diagram illustrating a gain-coupled DFB-LD according to a first embodiment.
【図２】実施例１の構造において、光吸収層の禁制帯幅
と誘導放出光の波長をエネルギーに換算した値との差Δ
Ｅgと、過飽和吸収が生じる頻度との関係を示す図であ
る。2 is a difference Δ between a band gap of a light absorption layer and a value obtained by converting the wavelength of stimulated emission light into energy in the structure of Example 1. FIG.
And E g, is a diagram showing the relationship between the frequency of supersaturation absorption occurs.
【図３】実施例２の利得結合ＤＦＢ−ＬＤを示す図であ
る。FIG. 3 is a diagram illustrating a gain-coupled DFB-LD according to a second embodiment.
【図４】実施例２の構造において、光吸収層の禁制帯幅
と誘導放出光の波長をエネルギーに換算した値との差Δ
Ｅgと、過飽和吸収が生じる頻度との関係を示す図であ
る。FIG. 4 shows the difference Δ between the band gap of the light absorption layer and the value obtained by converting the wavelength of stimulated emission light into energy in the structure of Example 2.
And E g, is a diagram showing the relationship between the frequency of supersaturation absorption occurs.
【図５】実施例３の利得結合ＤＦＢ−ＬＤを示す図であ
る。FIG. 5 is a diagram showing a gain-coupled DFB-LD of Example 3;
【図６】実施例３の構造において、光吸収層の禁制帯幅
と誘導放出光の波長をエネルギーに換算した値との差Δ
Ｅgと、過飽和吸収が生じる頻度との関係を示す図であ
る。FIG. 6 shows the difference Δ between the forbidden band width of the light absorption layer and the value obtained by converting the wavelength of stimulated emission light into energy in the structure of Example 3;
And E g, is a diagram showing the relationship between the frequency of supersaturation absorption occurs.
【図７】従来の利得結合ＤＦＢ−ＬＤを示す図である。FIG. 7 is a diagram showing a conventional gain-coupled DFB-LD.
【図８】光吸収層におけるキャリアの生成と消滅を説明
するための図である。FIG. 8 is a diagram for explaining generation and disappearance of carriers in the light absorption layer.
【図９】過飽和吸収が素子の特性に与える影響を説明す
るための図である。FIG. 9 is a diagram for explaining the effect of supersaturated absorption on the characteristics of the device.
【図１０】（ａ）ｎ型ＧａＡｓ、（ｂ）ｐ型ＧａＡｓの
吸収係数の光エネルギー依存性を示す図である。FIG. 10 is a diagram showing optical energy dependence of absorption coefficients of (a) n-type GaAs and (b) p-type GaAs.
１０１ ｎ−ＧａＡｓ基板 １０２ ｎ−ＡｌＧａＡｓ下クラッド層 １０３ ｕｎ−ＡｌＧａＡｓ活性層 １０４ ｐ−ＡｌＧａＡｓキャリアバリア層 １０５ ｐ−ＡｌＧａＡｓガイド層 １０６ ｎ−ＧａＡｓ光吸収層 １０７ ｐ−ＡｌＧａＡｓ上クラッド層 １０８ ｐ−ＧａＡｓコンタクト層 １０９ 窒化珪素絶縁膜 １１０ ｐ側電極 １１１ ｎ側電極 ３０１ ｎ−ＧａＡｓ基板 ３０２ ｎ−ＡｌＧａＡｓ下クラッド層 ３０３ ｕｎ−ＡｌＧａＡｓ活性層 ３０４ ｐ−ＡｌＧａＡｓキャリアバリア層 ３０５ ｐ−ＡｌＧａＡｓ第一ガイド層 ３０６ ｐ−ＡｌＧａＡｓ第二ガイド層 ３０７ ｐ−ＧａＡｓ光吸収層 ３０８ ｐ−ＡｌＧａＡｓ上クラッド層 ３０９ ｐ+−ＧａＡｓコンタクト層 ３１０ 窒化珪素絶縁膜 ３１１ ｐ側電極 ３１２ ｎ側電極 ５０１ ｎ−ＩｎＰ基板 ５０２ ｎ−ＩｎＰ第一下クラッド層 ５０３ ｎ−ＩｎＧａＡｓＰ光吸収層 ５０４ ｎ−ＩｎＰ第二下クラッド層 ５０５ ｕｎ−ＩｎＧａＡｓＰ活性層 ５０６ ｐ−ＩｎＰ上クラッド層 ５０７ ｐ+−ＩｎＧａＡｓコンタクト層 ５０８ 窒化珪素絶縁膜 ５０９，５１０ 電極 ７０１ ｎ−ＧａＡｓ基板 ７０２ ｎ−ＡｌＧａＡｓ下クラッド層 ７０３ ｕｎ−ＧａＡｓ活性層 ７０４ ｐ−ＡｌＧａＡｓキャリアバリア層 ７０５ ｐ−ＡｌＧａＡｓ第一ガイド層 ７０６ ｎ−ＧａＡｓ光吸収層 ７０７ 回折格子 ７０８ ｐ−ＡｌＧａＡｓ上第二ガイド層 ７０９ ｐ−ＡｌＧａＡｓ上クラッド層 ７１０ ｐ−ＧａＡｓコンタクト層101 n-GaAs substrate 102 n-AlGaAs lower cladding layer 103 un-AlGaAs active layer 104 p-AlGaAs carrier barrier layer 105 p-AlGaAs guide layer 106 n-GaAs light absorption layer 107 p-AlGaAs upper cladding layer 108 p-GaAs contact Layer 109 Silicon nitride insulating film 110 p-side electrode 111 n-side electrode 301 n-GaAs substrate 302 n-AlGaAs lower cladding layer 303 un-AlGaAs active layer 304 p-AlGaAs carrier barrier layer 305 p-AlGaAs first guide layer 306 p- AlGaAs second guide layer 307 p-GaAs light absorption layer 308 p-AlGaAs upper cladding layer 309 p + -GaAs contact layer 310 of silicon nitride insulating film 311 p-side electrode 312 n-side electrode 501 n- nP substrate 502 n-InP first lower cladding layer 503 n-InGaAsP light absorbing layer 504 n-InP second lower cladding layer 505 un-InGaAsP active layer 506 p-InP upper cladding layer 507 p + -InGaAs contact layer 508 of silicon nitride Insulating film 509,510 Electrode 701 n-GaAs substrate 702 n-AlGaAs lower cladding layer 703 un-GaAs active layer 704 p-AlGaAs carrier barrier layer 705 p-AlGaAs first guide layer 706 n-GaAs light absorption layer 707 Diffraction grating 708 Second guide layer on p-AlGaAs 709 Clad layer on p-AlGaAs 710 p-GaAs contact layer
Claims (5)
を備え、該周期構造が、前記活性層から発生する誘導放
出光に対する吸収係数が周期的に変化する、周期的吸収
層である利得結合分布帰還型半導体レーザにおいて、 前記誘導放出光のエネルギーｈνと、前記周期的光吸収
層の禁制帯幅Ｅgが、下記式（Ｉ）を満たしてなること
を特徴とする分布帰還型半導体レーザ装置。 【数１】 1. A gain, which is a periodic absorption layer, comprising a periodic structure for providing distributed light feedback in the vicinity of the active layer, and the periodic structure has a periodic absorption coefficient for stimulated emission light generated from the active layer. In the coupled distributed feedback semiconductor laser, the energy hν of the stimulated emission light and the forbidden band width E g of the periodic light absorption layer satisfy the following formula (I). apparatus. [Equation 1]
ｓ（０≦ｘ≦１）で形成され、 かつ、その厚さが電子のド・ブロイ波長よりも厚く、 かつ、前記誘導放出光のエネルギーｈνと前記周期的光
吸収層の禁制帯幅Ｅgとの差が０．１３ｅＶ以上である
ことを特徴とする請求項１に記載の分布帰還型半導体レ
ーザ装置。2. The periodic light absorption layer comprises n-type Al x Ga 1 -x A
s (0 ≦ x ≦ 1), the thickness thereof is thicker than the de Broglie wavelength of electrons, and the energy hν of the stimulated emission light and the forbidden band width E g of the periodic light absorption layer are 2. The distributed feedback semiconductor laser device according to claim 1, wherein the difference between the distributed feedback semiconductor laser device and the distributed feedback semiconductor laser device is 0.13 eV or more.
ｓ（０≦ｘ≦１）で形成され、 かつ、その厚さが電子のド・ブロイ波長よりも厚く、 かつ、前記誘導放出光のエネルギーｈνと前記周期的光
吸収層の禁制帯幅Ｅgとの差が０．０８ｅＶ以上である
ことを特徴とする請求項１に記載の分布帰還型半導体レ
ーザ装置。3. The periodic light absorbing layer is p-type Al x Ga 1 -x A
s (0 ≦ x ≦ 1), the thickness thereof is thicker than the de Broglie wavelength of electrons, and the energy hν of the stimulated emission light and the forbidden band width E g of the periodic light absorption layer are 2. The distributed feedback semiconductor laser device according to claim 1, wherein the difference between and is 0.08 eV or more.
ｓ1-zＰz（０≦ｙ≦１、０≦ｚ≦１）で形成され、 かつ、その厚さが電子のド・ブロイ波長よりも厚く、 かつ、前記誘導放出光のエネルギーｈνと前記周期的光
吸収層の禁制帯幅Ｅgとの差が０．１５ｅＶ以上である
ことを特徴とする請求項１に記載の分布帰還型半導体レ
ーザ装置。Wherein said periodic light absorption layer is n-type In 1-y Ga y A
s 1-z P z (0 ≦ y ≦ 1, 0 ≦ z ≦ 1), and its thickness is thicker than the de Broglie wavelength of electrons, and the energy hν of the stimulated emission light and The distributed feedback semiconductor laser device according to claim 1, wherein a difference from the forbidden band width E g of the periodic light absorption layer is 0.15 eV or more.
ｓ1-zＰz（０≦ｙ≦１、０≦ｚ≦１）で形成され、 かつ、その厚さが電子のド・ブロイ波長よりも厚く、 かつ、前記誘導放出光のエネルギーｈνと前記周期的光
吸収層の禁制帯幅Ｅgとの差が０．１ｅＶ以上であるこ
とを特徴とする請求項１に記載の分布帰還型半導体レー
ザ装置。Wherein said periodic light absorption layer is p-type In 1-y Ga y A
s 1-z P z (0 ≦ y ≦ 1, 0 ≦ z ≦ 1), and its thickness is thicker than the de Broglie wavelength of electrons, and the energy hν of the stimulated emission light and The distributed feedback semiconductor laser device according to claim 1, wherein a difference from the forbidden band width E g of the periodic light absorption layer is 0.1 eV or more.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP06256095A JP4017196B2 (en) | 1995-03-22 | 1995-03-22 | Distributed feedback semiconductor laser device |
| US08/621,748 US5852625A (en) | 1995-03-22 | 1996-03-22 | Distributed feedback semiconductor laser |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP06256095A JP4017196B2 (en) | 1995-03-22 | 1995-03-22 | Distributed feedback semiconductor laser device |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH08264879A true JPH08264879A (en) | 1996-10-11 |
| JP4017196B2 JP4017196B2 (en) | 2007-12-05 |
Family
ID=13203794
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP06256095A Expired - Fee Related JP4017196B2 (en) | 1995-03-22 | 1995-03-22 | Distributed feedback semiconductor laser device |
Country Status (2)
| Country | Link |
|---|---|
| US (1) | US5852625A (en) |
| JP (1) | JP4017196B2 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH10223966A (en) * | 1997-01-31 | 1998-08-21 | Sharp Corp | Gain coupled distributed feedback semiconductor laser |
Families Citing this family (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6121634A (en) * | 1997-02-21 | 2000-09-19 | Kabushiki Kaisha Toshiba | Nitride semiconductor light emitting device and its manufacturing method |
| EP1089407A1 (en) | 1999-09-30 | 2001-04-04 | The Furukawa Electric Co., Ltd. | Gain-coupled distributed-feedback semiconductor laser device |
| US6574256B1 (en) | 2000-01-18 | 2003-06-03 | Xerox Corporation | Distributed feedback laser fabricated by lateral overgrowth of an active region |
| EP1265326B1 (en) * | 2000-03-13 | 2009-05-13 | Sharp Kabushiki Kaisha | Gain-coupled distributed feedback semiconductor laser device and production method therefor |
| US6696311B2 (en) * | 2001-05-03 | 2004-02-24 | Spectra-Physics Semicond. Lasers, In | Increasing the yield of precise wavelength lasers |
| JP2003133638A (en) * | 2001-08-14 | 2003-05-09 | Furukawa Electric Co Ltd:The | Distributed feedback semiconductor laser element and laser module |
| JP5099948B2 (en) * | 2001-08-28 | 2012-12-19 | 古河電気工業株式会社 | Distributed feedback laser diode |
| US6903379B2 (en) * | 2001-11-16 | 2005-06-07 | Gelcore Llc | GaN based LED lighting extraction efficiency using digital diffractive phase grating |
| US20030235225A1 (en) * | 2002-06-22 | 2003-12-25 | Rick Glew | Guided self-aligned laser structure with integral current blocking layer |
| JP2005166998A (en) * | 2003-12-03 | 2005-06-23 | Mitsubishi Electric Corp | Ridge-type distribution feedback semiconductor laser |
| DE102008054217A1 (en) * | 2008-10-31 | 2010-05-06 | Osram Opto Semiconductors Gmbh | Optoelectronic semiconductor chip and method for producing an optoelectronic semiconductor chip |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2705409B2 (en) * | 1991-11-21 | 1998-01-28 | 三菱電機株式会社 | Semiconductor distributed feedback laser device |
| JPH067624A (en) * | 1992-06-26 | 1994-01-18 | Mitsubishi Heavy Ind Ltd | Adsorption device |
| US5539766A (en) * | 1993-08-19 | 1996-07-23 | Matsushita Electric Industrial Co., Ltd. | Distributed feedback semiconductor laser |
-
1995
- 1995-03-22 JP JP06256095A patent/JP4017196B2/en not_active Expired - Fee Related
-
1996
- 1996-03-22 US US08/621,748 patent/US5852625A/en not_active Expired - Lifetime
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH10223966A (en) * | 1997-01-31 | 1998-08-21 | Sharp Corp | Gain coupled distributed feedback semiconductor laser |
Also Published As
| Publication number | Publication date |
|---|---|
| US5852625A (en) | 1998-12-22 |
| JP4017196B2 (en) | 2007-12-05 |
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